Played By: Megan Fox
- Alpha Bitch: She's a popular cheerleader who's also a massive bitch, to the point where the other students consider her "evil." Despite this, guys trip over themselves to impress her. She does have shades of a nicer side, at least at first, but only to Needy.
- Ambiguously Bi: Much like Needy, she shows many traits of this, actually trying to (and succeeding at) seduce her at one point. She also utters this great line:Needy: I thought you only killed boys!Jennifer: I go both ways.
- Deconstructed by Word of God. Megan Fox says that she played Jennifer as a deeply closeted lesbian.
- Cursed with Awesome: She seems to think so after becoming possessed by the demon, but in reality it's Blessed with Suck.
- Decoy Protagonist: Her name may be in the title, but the story is about Needy.
- Enemy to All Living Things: Subverted. The animals are drawn to her.
- Fanservice: She provides both this and Fan Disservice.
- For the Evulz: When she could've eaten any other guy, she killed Chip to hurt Needy.
- Horror Hunger: Averted. She adapts to her new diet very well.
- I'm a Humanitarian: Post-possession, she has to eat the people she kills. If her attempts at eating a roast chicken are any indication, she literally can't eat anything else.
- Jerkass: More so in the post demonic possession.
- Literal Maneater: She seduces men, luring them in with the promise of sex... and then kills them and eats their remains.
- Ms. Fanservice: Of course. It's Megan Fox!
- Romantic Two-Girl Friendship: She's in one with Needy, but it's a little bit more twisted than usual.
Anita "Needy" Lesnicki
Played By: Amanda Seyfried
- Ambiguously Bi: Has a boyfriend, whom she cares about very deeply. She also makes out with Jennifer, and seems to be really into it before she breaks it off.
- Berserk Button: Don't tell her what to eat. An orderly lost a tooth when she recommended she eat more than Toastems.
- Dumb Blonde: Inverted. She's incredibly smart.
- Hollywood Homely: Invoked. Needy has to be more plain around Jennifer.
- Only Known by Their Nickname: No one ever calls her "Anita."
- Shipper on Deck: She ships Jennifer/Colin, and encourages Jennifer to go out with him. This doesn't end well.
- Took a Level in Jerkass: She becomes extremely violent and unstable after being well and truly broken. The How We Got Here opening has her kicking an orderly (whose only "crime" was to chastise Needy for her choice of food) so hard she knocks one of her teeth out.Needy: "I recommend that you shut the fuck up!"
Played By: Johnny Simmons
- Nice Guy: He's kind and supportive of Needy, and seems to get along well with everyone except Jennifer.
Played By: Adam Brody
- Greater-Scope Villain: His sacrifice of Jennifer made her what she became.
Played By: Kyle Gallner
- Emo/Goth: He has the hairstyle and wears makeup and has piercings. Needy describes him as "dark and emotional".
- Nice Guy: Despite his goth sensibilities, he's very friendly, and is good friends with Needy.
Played By: J. K. Simmons